Extensive systems have been deployed to use GPS (Global Positioning System) capabilities for the purpose of tracking vehicle fleets of, e.g., truck trailers, truck tractors and/or trucks; or railcars; or fleets of cargo containers. Such systems have been referred to as “asset tracking systems” and deploy asset tracking units designed to be attached to individual vehicles. Each asset tracking unit typically includes a GPS receiver that is capable of receiving GPS signals from a plurality of GPS satellites and determining the unit's location based on the GPS signals. Upon obtaining a position fix, the asset tracking unit may report the unit's location via satellite communication (using another set of satellites) or the like to a central station. With such a system, the proprietor of the vehicle fleet may have close to real-time information concerning the whereabouts of all vehicles in the fleet. This may lead to significant efficiencies in planning and managing assignments of vehicles to particular tasks. In addition, an asset tracking system of this type may help in the detection of, and response to, irregularities such as theft of vehicles or their contents.
It has been proposed to install one or more sensors in or on a vehicle with the sensor(s) interfaced to the asset tracking unit assigned to the vehicle. The sensor(s) may detect changes in conditions related to the vehicle such as opening or closing of a door of a vehicle, loading or unloading of cargo in or from the vehicle and (where the vehicle is a truck trailer) coupling or de-coupling of the vehicle to or from a truck tractor. The sensor(s) may provide signals indicative of such events to the asset tracking unit, which may then report the events to the central station to increase the amount of information about operation of the vehicle that is present in the asset tracking system. In at least some cases, the system may notify a user/attendant of the events, and the user/attendant may take steps to respond to the events.
Potential disadvantages of reporting and responding to events in an asset tracking system may involve expenditure of resources such as battery power capacity of the asset tracking units, use of satellite communication systems and charges for such use, and attendant time and attention for receiving reports of events and/or responding to such reports.